4-Nitrobenzimidazole → 7-Aminobenzimidazole

Participants

Reaction Steps

4-Nitro-1H-benzimidazole was hydrogenated (48 psi) with 1 g 10% Pd/C in HOAc (100 mL) for 3 h. The crude mixture was filtered through a pad of Celite, washing with MeOH, and concentrated. The residue was taken up in 2 M aq HCl and applied to a Phenomenex Strata-X-C ion exchange column (5 g). The column was washed with H20 and MeOH, The washings contained additional material and were applied to another Strata X-C ion exchange column (5 g). The columns were washed with H20 and MeOH. Each of the columns containing product were washed separately with 10% concentrated NH4OH in MeOH and the product collected in fractions. The collected fractions were concentrated to give 1H-Benzimidazol-4-amine as a deep red solid. 1H NMR (500 MHz, d6-DMSO) δ 12.10 (bs, 1H), 7.98 (s, 1H), 6.87 (t, J=7.81 Hz, 1H), 6.72 (d, J=7.82 Hz, 1H), 6.34 (d, J=7.57 Hz, 1H), 5.16 (bs, 2H).

Provenance & Evidence